1. Field of the Invention
This invention relates to a probe for an intraluminal ultrasonic scanner, and more particularly to a probe which is inserted into a lumen of a patient so that a transducer therein can scan to provide an ultrasonic tomography of the patient.
2. Description of the Prior Art
Most conventional ultrasonic tomographs are obtained by rediating ultrasonic pulses into the body from the body surface, and by receiving the reflected waves therefrom to obtain information on the inside of the body. Recently, intraluminal tomography in which an ultrasonic probe is inserted into a body cavity and ultrasonic pulses are transmitted to and received from near the organs in a living body has been drawing increasing attention. This method of intraluminal tomography is characterized in that a higher resolution with high frequencies can be obtained because there is less damping of sound waves due to subcutaneous fat layers between the target organ and the probe.
Transrectal tomography is particularly effective for diagnosis related to the prostate, and various apparatuses for this tomography have been proposed in the past. On the other hand, various proposals have also been made for an apparatus for diagnosis concerning the walls of the stomach, the pancreas, and the like, that is, a so-called "echo endoscope". Japanese Patent Laid-Open No. 1984/1979, for example, discloses an apparatus in which a fiber scope and a ultrasonic transducer are assembled into a single probe, and which enables both observation of the surfaces of internal walls and tomography within those walls.
The most ordinary type of this intraluminal ultrasonic scanner is one in which a transducer is mechanically rotated within a probe to obtain a radial tomogram. A problem encountered in this mechanical scanning transducer concerns the size and shape of the transducer. In the prior art in the Japanese Patent Laid-Open document quoted above, a round transducer is used, but there is a limit on the inner diameter of the probe. The lateral resolution in ultrasonic tomography is inversely proportional to the diameter of the transducer, and hence the resolution drops if the diameter of the round transducer is reduced, such as in the prior art described above. In addition, since the sensitivity of the probe is substantially proportional to the sound-wave transmission and reception area of the transducer, the sensitivity drops and the depth that can be observed is less if the diameter of the round transducer is reduced.